Various devices of this type have been proposed in the past. In a first group best exemplified by U.S. Pat. Nos. 1,238,461 Bourdelat, 2,980,994 Stachon, and 3,138,870 Stachon, a rotating blade is mounted across the vacuum flow channel. A second group of such clippers as disclosed in U.S. Pat. Nos. 1,730,889 Hoberecht, 3,979,825 Baumann, 4,077,122 Rollor, Jr. et al., and 4,188,720 Korf uses oscillating blades, the latter with the added improvement of translating movement of the oscillating blade across the hair flow channel. The avowed object of such an improvement was to cause a straight alignment of the hair under the vacuum pull and an even cutting to a constant length. The Korf approach requires a complex mechanism and suffers from the fact that large quantities of hair drawn into the vacuum channel, when attacked by the advancing blade may bunch up and bend away from the blade. This may result in a very uneven clipping of some of the hair. The translating movement of the blade carriage takes time and consumes a great deal of energy.
In some of the earlier devices the rotary blades interfered with the regular flow of hair through the housing, causing pulsation and turbulence which prevented the proper alignment of the hair.
An improved clipper is disclosed in my U.S. Pat. No. 4,679,322 wherein the oscillating blades are not translated and are configured to avoid interruption of the hair flow.